This makes four custom hearts with text. The text can be one line or two lines. To make two lines of text you separate the upper line and the lower line with a slash "/".
Updated 12 / 1 / 2018 to add an optional necklace hole.
There is a bit of...

If you go to Thingiverse you can use the customizer app to place 4 messages on 4 hearts. These will then be in .stl format. If you have a package like Vectric’s Vcarve Desktop, you can create the tool paths to carve these out. The app has an option to put a hole in the heart so that you can make it into a necklace.

Candy hearts, as noted above, seem easy and obvious and like something that would sell.

Lots of SVG files out there of roses … carve in red oak, reddish stain and some tung oil … could be a trivet or whatever. Could even do a carve of a dozen roses arranged on a circle. With a V bit, I think it would go pretty quick.

Any other ideas I have get complex, like small wooden boxes to put chocolates or jewelry or whatever into.

I think a way to go and maybe sell even better is to go snarky or a little bit against the Valentines Day grain. Not hateful, but tweak it a bit. I’m thinking of the coffee mug a co-worker has that says, “Have a happy whatever doesn’t offend you.”

So I’m picturing a heart or flower or whatever that says something like, “This hereby certifies my acknowledgement of this and all future Saint Valentine’s Days.”